A battery management system (“BMS”) stops a Li-ion battery pack from output after the battery is over discharge. However, the BMS is powered by the Li-ion battery, thus, the continued work of the BMS will hurt the battery without timely charging in the state of discharge. Ordinarily, the customer should cut the BMS manually, while the intelligent BMS will detect the charger in the state of discharge, if the charger is not connected, the BMS will cut itself to reduce power consumption. And if the charger is detected in the power-off state, the BMS will be restarted. The BMS wake-up circuit is required to restart the BMS when detecting the charger in charging the battery pack.
The regular method is spanning the sampling circuit between the battery anode P+ and cathode P−, or connecting a detection circuit at both ends of the charging MOSFET to wake up the BMS. However, the first one is always in working condition and costs much power of the battery; and the second one demands on voltage sharply, the bad voltage or current will burn the detection circuit.
Connecting photocoupler directly to both ends of the charger is also a common charging detection circuit. This detection circuit is very simple with poor withstand capability. In addition, it costs power when the charger is offline and damages the battery pack. Connecting a detection circuit reversely to both ends of the charge relay is another choice. However, this circuit is hard to control and easy to burn itself.